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Harmful algal blooms worry anglers, threaten fisheries

Copyright 2000 The Federal Capital Press of Australia Pty Limited

The Canberra Times

August 17, 2000

BYLINE: JOHN TURNBULL

The recent alarming increase of algal blooms, red tides and phytoplankton blooms common names for the recent explosive increase of what scientists are calling harmful algal blooms are worrying anglers.

For HABs not only have catastrophic effects on fish but are also extremely hazardous to other wildlife and humans. There seem to be two reasons for their proliferation. One is increased ultra-violet radiation reaching earth following the thinning of the ozone layer from air-borne pollutants. This is killing the tiny insects which normally graze on algae in freshwater.

The other is the dramatic increase in nutrients entering both fresh and salt water due to land clearing and the accompanying soil erosion.

HAB researcher Rosemary Paxinos of Flinders University says as well as killing fish and wildlife, HABs cause narcosis, respiratory distress, cramping, vomiting, autonomic nervous system dysfunction (causing rages and personality changes) cognitive impairment and short term memory loss.

Some HAB toxins are quickly absorbed through the skin, producing immediate symptoms which can reoccur years later.

Algal blooms are now common around Canberra, especially in Burrinjuck Dam, as well as local lakes and the nearby Murrumbidgee. Since Canberra is near the headwaters of the Murrumbidgee, which is a major part of the vast Murray-Darling Basin covering nearly a third of the continent, this is an alarming indication of something dramatically wrong.

HABs often follow the establishment of fish farms due to increased nutrients in the water from waste food and fish excreta.

Nutrients flowing from a trout farm upstream from Cooma were believed responsible for a blue-green algae bloom which caused the hospitalisation of Cooma residents in 1998.

The recent construction of a sewage works on a tributary of the Hawkesbury which I've fished extensively for half a century was followed by a dramatic increase in algae and weed growth.

Within two years the platypus and kingfishers were gone, as were the freshwater herring, catfish and mullet. Bass continue to enter it during floods, but soon develop lesions and then vanish from the section downstream of the sewage works.

The danger to wildlife and humans posed by HABs seems reason enough for a rapid move away from harmful land-clearing practices, aquaculture and the use of freshwater streams as sewers.

Most anglers believe Canberra's sewage should not be emptied into the Murrumbidgee River and thus into Burrinjuck Dam.

ANGLERS have discovered a new fishing method at the edge of the continental shelf east of Narooma.

Dropping baits on fine, non-stretch spiderwire to the bottom some 300m down is producing good catches of large blue-eyed trevalla and other species. The fear is that the method will be exploited by commercial fishers.

There are big schools of bonito at Montague Island and some patches of kingfish. The reefs are producing reasonable but unexciting numbers of snapper and morwong. The beaches are fairly lively for salmon and tailor.

Wagonga has plenty of leatherjackets and lots of visible but hard-to- catch blackfish. Cold weather has been keeping anglers away, but the few who have been fishing say the best action is on large bream among the oyster leases at the upper end.

Whittakers Creek has been producing good bream and has big schools of both poddy and bull mullet, but the water's so clear it's hard to get near them, to the disgust of local flyfishers who are discovering clearwater mullet can be as shy as trout.